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The morphologies of massive galaxies from z ~ 3-witnessing the two channels of bulge growth



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Huertas Company, M. and Pérez González, Pablo Guillermo and Mei, S. and Shankar, F. and Bernardi, M. and Daddi, E. and Barro, G. and Cabrera Vives, G. and Cattaneo, A. and Dimauro, P. and Gravet, R. (2015) The morphologies of massive galaxies from z ~ 3-witnessing the two channels of bulge growth. Astrophysical journal, 809 (1). ISSN 0004-637X


Official URL: http://dx.doi.org/10.1088/0004-637X/809/1/95



We quantify the morphological evolution of z ~ 0 massive galaxies (M_*/M_∼ ∼10^11.2 +/- 0.3) from z ~ 3 in the 5 CANDELS fields. The progenitors are selected using abundance matching techniques to account for the mass growth. At z < 1, the population matches the massive end of the Hubble sequence, with 30% of pure spheroids, 50% of galaxies with equally dominant disk and bulge components, and 20% of disks. At z ~ 2-3 however, there is a majority of irregular systems (~ 60%-70%) with still 30% of pure spheroids. We then analyze the stellar populations, star formation rates (SFRs), gas fractions, and structural properties for the different morphologies independently. Our results suggest two distinct channels for the growth of bulges in massive galaxies. Around ~ 30%-40% were already bulges at z ~ 2.5, with low average SFRs and gas fractions (10%-15%), high Sersic indices (n > 3-4), and small effective radii (R_e ∼1 kpc), pointing toward an even earlier formation through gas-rich mergers or violent disk instabilities. Between z ~ 2.5 and z ~ 0, they rapidly increase their size by a factor of ~ 4-5, are quenched, and slightly increase their Sersic indices (n ~ 5) but their global morphology remains unaltered. The structural evolution is independent of the gas fractions, suggesting that it is driven by ex situ events. The remaining 60% experience a gradual morphological transformation, from clumpy disks to more regular bulge +disk systems, essentially happening at z > 1. This results in the growth of a significant bulge component (n ~ 3) for 2/3 of the systems, possibly through the migration of clumps, while the remaining 1/3 retain a rather small bulge (n ~ 1.5-2). The transition phase between disturbed and relaxed systems and the emergence of the bulge is correlated with a decrease in the star formation activity and the gas fractions, suggesting a morphological quenching process as a plausible mechanism for the formation of these bulges.

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© 2015. The American Astronomical Society. We would like to thank the referee for a useful and constructive report that clearly helped in improving the manuscript. M.H.C. warmly thanks P. Behroozi for kindly sharing the mass growth and merger rates of massive galaxies used in this paper. P.G.P.-G. acknowledges funding from Spanish Government MINECO Grant AYA2012-31277. G. C. V. gratefully acknowledges funding from CONICYT (Chile) through their Doctoral Scholarship. This work has made use of the Rainbow Cosmological Surveys Database, which is operated by the Universidad Complutense de Madrid (UCM), partnered with the University of California Observatories at Santa Cruz (UCO/Lick, UCSC). This work is based on observations taken by the 3D-HST Treasury Program (GO 12177 and 1232) with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc, under NASA contract NAS5-26555.

Uncontrolled Keywords:Goods nicmos survey; Star-forming galaxies; Extragalactic legacy survey; Compact quiescent galaxies; Hubble-space-telescope; Greater-than 1; Size evolution; High-redshift; Intermediate redshift; Structural evolution
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:33794
Deposited On:27 Oct 2015 14:12
Last Modified:10 Dec 2018 15:05

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